Field of the Invention
The invention relates to a delivery for a printing machine that processes sheets passing through the latter in a processing direction, including sheet brakes which are adjustable transversely to the processing direction, and which, respectively, are made up of a braking element having a vacuum passing therethrough, the braking element being cooperatable with the sheet and revolving during the operation thereof, and sheet supports adjustable transversely to the processing direction. The invention also relates to a sheet-processing printing machine equipped with a delivery of the foregoing type.
A delivery of the type referred to in the introduction hereto is disclosed by the German Published Non-prosecuted Patent Application (DE-OS) 26 27 812. The braking elements disclosed therein, which revolve when operating, are made up of suction wheels which are constructed in the form of hollow wheels. A respective hollow wheel is mounted on a journal of a suction-wheel holder. As the hollow wheel revolves during operation, a cylindrical inner surface of the hollow wheel slides over a contact surface of the suction-wheel holder. A borehole formed in the contact surface is connected to a suction pipe and communicates with radial boreholes formed in the hollow wheel, the radial boreholes succeeding one another in the peripheral direction of the hollow wheel, so that the braking element, constructed in the form of the hollow wheel, is traversed by a vacuum that prevails in the suction pipe. In order to adjust the sheet brakes formed by the suction wheels transversely to the processing direction, the suction-wheel holders are pushed onto a cross member arranged transversely to the processing direction, and can be fixed by setscrews in a respectively required position with regard to the cross member. In order to drive the suction wheels, a shaft with a square cross section which passes through the suction-wheel holders is provided, and engages in a form-locking manner in the hub region of a respective suction wheel. In this regard, it is noted that a form-locking connection is one which connects two elements together due to the shape of the elements themselves, as opposed to a force-locking connection, which locks the elements together by force external to the elements.
The sheet supports provided in the heretofore known delivery are connected in a form-locking manner to the aforementioned so-called square shaft and are displaceable along the square shaft by applying an adjusting force that overcomes a frictional connection between the shaft and the sheet supports, so that the sheet supports are likewise adjustable transversely to the processing direction. A respective sheet support is formed by a pair of carrying disks which are spaced apart from one another and provide a rotational mounting for satellite spur wheels distributed over the periphery thereof and projecting beyond the carrying disks.
In particular, when a printing machine is operating in a recto/verso or first-form and perfecter printing process mode, the sheet brakes can be placed so that the braking elements act only upon print-free corridors of the sheets to be braked. For the case wherein, during a printing job, the sheets have fewer print-free corridors, which are of adequate width for a braking element to act, than sheet brakes, it is not possible to use all of the latter. It is apparent for such a case that, with the aforementioned heretofore known delivery, provision is made to connect the suction wheels selectively to a suction pipe and to a compressed-air pipe, respectively, so that apparently through the intermediary of blown air flowing out of a suction wheel, contact between the suction wheel and the sheet is avoided when there is no print-free corridor of the sheets opposite the suction wheel. This appears to be problematic, however, particularly in the case of rapidly succeeding sheets, inasmuch as those sheets normally have powerful blown-air flows applied thereto on the side thereof facing away from the sheet brakes, specifically in order to achieve a rapid lowering of the sheets released from the sheet brakes and, thus, to avoid collisions between the successive sheets. It is therefore suggested rather to remove the superfluous sheet brakes from the area over which the sheets sweep.
For the case wherein the sheets have a format that is smaller than the maximum format printable by the printing machine, if necessary or desirable, the superfluous sheet brakes outside the format can be moved into a parking position, if disassembly is not an acceptable alternative. A given outlay for disassembly and assembly has already been incurred for this purpose, inasmuch as the sheet supports which are in the way of any displacement of sheet brakes from the area over which the sheets sweep into a position outside the area, initially have to be disassembled and reassembled after the displacement of the sheet brakes has occurred.
In the case of printing sheets with the maximum possible format for the printing machine, however, if a given number of sheet brakes prove to be superfluous, generally these cannot be displaced into a position outside the format, so that they either have to be disassembled or brought reliably out of contact with the sheets in another way. A measure that is suitable therefor and is an alternative to disassembly, and to which recourse is certainly had in practice, includes, for example, the provision of additional sheet supports, specifically in the form of conventional spur-wheel arrangements, on either side of a superfluous sheet brake and closely adjacent to the latter. However, in this type of application thereof, these sheet supports must project beyond the sheet brake in the direction of the sheets. In this regard, however, a given marking of the printed image by the spur-wheel arrangements generally has to be taken into account.
In any case, however, a relatively high outlay is needed to implement the arrangement of the sheet brakes and of the sheet supports required for a respective printing job.
Furthermore, it is apparent from the arrangement of the sheet brakes and the sheet supports provided in the aforementioned delivery, that these can impede one another during the adjustment thereof transversely to the processing direction. Although this could be countered by providing only a very small number of sheet supports, the consequence thereof would be that it would not be possible to print at the high processing speed that is common in modern printing machines. This is because, in this case, due to the powerful blown-air flows, which are required in this case and have already been mentioned, on that side of the respective sheets which faces away from the sheet brakes, there would result a relatively large amount of sagging of the sheets between the sheet brakes, with the risk of smearing the printed image on that side of the respective sheets which faces the sheet brakes.
It is accordingly an object of the invention to provide a printing-machine delivery of the general type mentioned in the introduction hereto that is configured in such a manner that the sheet brakes and sheet supports thereof are adaptable to different printing jobs with a relatively low outlay or expense for conversion.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a delivery for a printing machine that processes sheets passing through the latter in a processing direction, comprising sheet brakes adjustable transversely to the processing direction and, respectively, including a braking element having a vacuum passing therethrough, the braking element being cooperatable with the sheet and revolving during the operation thereof, and a supporting element through which vacuum does not pass, the respective braking element being replaceable by the supporting element for converting one of the sheet brakes to a respective sheet support adjustable transversely to the processing direction.
In accordance with another feature of the invention, the delivery includes a plurality of the sheet brakes and the sheet supports, the sheet brakes and the sheet supports being servomotively adjustable.
In accordance with a further feature of the invention, a respective braking element is formed as an endless suction belt, and a respective supporting element is formed as an endless supporting belt, the supporting belt having a cross section forming an elevation or rise on the outside of the supporting belt.
In accordance with another aspect of the invention, there is provided a sheet-processing printing machine, comprising a delivery having at least one of the foregoing features.
A configuration of the foregoing type according to the invention shortens from many points of view the fitting time for adapting the sheet brakes and the sheet supports to the respective printing job; specifically, in order to implement the functions of braking the sheets, on the one hand, and the support of the sheets, on the other hand, it is only necessary to replace a functional part on one of otherwise identical basic functional units, and superfluous sheet brakes, if appropriate, do not need to be disassembled, because sheet brakes and sheet supports can be formed in any desired sequence transversely to the processing direction. For example, a basic functional unit constructed as a sheet brake, in a preceding print job can be converted, if required, into a sheet support or, while maintaining the function thereof, can be displaced from a previously assumed position thereof into a different position, while a sheet brake previously positioned at a different location, can assume a position which has become free, and thereat, after the braking element thereof has been replaced by a supporting element, can act as a sheet support.
One development provides for the sheet brakes and the sheet supports to be servomotively adjustable. This is possible as a result of the configuration according to the invention, without risk of mutual collision, because the succession of sheet brakes and sheet supports transversely to the processing direction can be selected as desired, due to the ability of the basic functional units to be converted.
In a preferred refinement, a respective braking element is formed as an endless suction belt, and a respective supporting element is formed as an endless supporting belt, and the supporting belt has a cross section which forms an elevation or rise on the outside of the supporting belt. In this case, it is further preferred for both the suction belt and the supporting belt to be elastic in the peripheral direction thereof and dimensioned so that when these belts are mounted or assembled, without using a tensioning device, they are set under a tension in the peripheral direction that is adequate for the intended use of the suction or supporting belt.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a delivery for a printing machine, and a printing machine equipped with such a delivery, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: